Hillary Clinton has lost some ground in personal favorability this year, but continues to outpace both Barack Obama and, by a wide margin, Marco Rubio - like Clinton, a possible successor to Obama - in this basic measure of public popularity.

Six in 10 Americans in the latest ABC News/Washington Post poll see Clinton favorably, down 6 percentage points from her career high in January. Obama's seen favorably by 53 percent, down 7 points from January and back to his pre-re-election level across most of 2012.

Rubio, a Republican U.S. senator from Florida involved in the immigration reform effort, is far less known on the national stage. Half of Americans express no opinion of him at all, similar to its level last August, when he first was being mooted as a possible presidential candidate. The rest divide evenly on Rubio in this poll, produced for ABC by Langer Research Associates.

The single-digit comedowns for Obama and Clinton are unsurprising. Since his re-election, the president's waded into contentious policy areas such as gun control and immigration, while dealing with the Internal Revenue Service and National Security Administration controversies. Obama's job approval likewise is off from his post-election high in ABC/Post polls.

Clinton, for her part, has stepped away from her popular role as secretary of state and may be seen in an increasingly partisan light given wide discussion of her possible candidacy for the Democratic presidential nomination in 2016. Last week she said she hopes to see a woman president, and, even without being a formal candidate, was endorsed by Sen. Claire McCaskill (D-Missouri). A campaign fundraising committee has been created to support Clinton (without her endorsement), as has one to oppose her.

GROUPS - Indicating increased partisanship, Clinton's popularity since January has dropped by 10 points among Republicans and among "somewhat" conservative Americans; she's also lost 9 points among whites, 10 points among seniors and 11 points among college graduates.

Obama, on the other hand, has lost ground disproportionately among some key Democratic-leaning groups, down 12 points in favorability among liberals, 10 points among those without a college degree, and 9 points each among nonwhites and people with household incomes less than $50,000 a year. His favorable rating also is down 11 points among independents, dipping just below the halfway mark.

While Rubio retains a broad recognition deficit, partisan divisions about him have lessened from last August, with negative views among Democrats down by 13 points and positive views among Republicans down by 11 points. His support for immigration reform - a cause more popular among Democrats than among Republicans - may be a factor.

METHODOLOGY - This ABC News/Washington Post poll was conducted by landline and cell phone June 19-23, 2013, in English and Spanish, among a random national sample of 1,010 adults. Results have a margin of sampling error of 3.5 points. The survey was produced for ABC News by Langer Research Associates of New York, N.Y., with sampling, data collection and tabulation by SSRS/Social Science Research Solutions of Media, Pa.